Various forms of devices heretofore have been provided for selective operation of an eight cylinder engine on only four cylinders thereof, a six cylinder engine on only three cylinders thereof and a two cylinder engine on only one cylinder thereof. Some of these previous devices are used in conjunction with combustion engines including at least two individual intake manifold air and fuel passages for supplying a fuel and air charge to separate sets of cylinders of the engine and function to selectively block one of the air and fuel passages whereby the engine will operate on only one-half the number of cylinders included in the engine. However, these previously known structure have been inoperative to readily alternate the air and fuel passage to be blocked and have further been inoperative to effect such alternate blocking of air and fuel passages automatically. Accordingly, a need exists for an improved apparatus and method for alternately blocking separate air and fuel intake passages of the intake manifold of a multicylinder combustion engine.
Examples of various forms of previously known structures for limiting operation of a combustion engine to operation of only one-half of cylinders thereof and which include some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 2,166,968, 2,918,047, 4,019,479, 4,109,634, 4,130,102, 4,198,940 and 4,201,179.